1. Field of the Invention
The present invention relates to methods of manufacturing a rotor core arranged in the central portion of a motor-driven valve, which is used for controlling flow rate of fluid such as refrigerant for a refrigeration cycle system and is provided with a valve body linearly moving by rotation of a rotor; a rotor feed screw for moving the rotor through engagement with the rotor; and the rotor.
2. Description of the Related Art
One of the motor-driven valves described above is proposed in Japanese Patent 3310042. As shown in FIG. 6, the motor-driven valve 50 comprises: a valve main body 55 having a first passage 52 and a second passage 53 that communicate with a valve chamber 51, and a valve seat 54 at a portion of the second passage 53 that communicates with the valve chamber 51; a rod-shaped needle valve 57 that contacts with and is separated from a valve seat portion 56 of the valve main body 55; a cylindrical sealed case 59; a stator coil 67 disposed outside the sealed case 59; a rotor 64 that rotates in the sealed case 59 through magnetization by feeding current of the stator coil 67 so as to be movable in a valve opening/closing direction and has a cylindrical sleeve 62 and a cylindrical permanent magnet 63 fixed on an outer surface of the sleeve 62 through a stop ring 66; and a male screw pipe 61 allowing the needle valve 57 to act for valve opening/closing operation through screw-feeding action by rotation of the rotor 64, wherein a lower case 60 of the sealed case 59 is fixed through welding to the valve main body 55.
In the motor-driven valve 50, as shown in FIGS. 6 and 7B, a valve closing limit stopper 62a projects on the lower end portion of the sleeve 62, and as shown in FIGS. 6 and 8B, a full-closed stopper 58a projects on a flange body 58, and when the needle valve 57 is closed, the valve closing limit stopper 62a abuts the full-closed stopper 58a as shown in FIG. 6, which restricts the rotor 64 from further lowering at the closed state of the valve 50.
At the restriction of the rotor 64 from lowering, the distance h4 shown in FIG. 7B between the lower end of a bushing 68 and the lower end of the valve closing limit stopper 62a is set to be integer times as the pitches of a female screw 68a, and the distance h5 shown in FIG. 8B between the upper end of the male screw pipe 61 and the upper end of the full-closed stopper 58a is set to be integer times as the pitches of a male screw 61a plus a half pitch, and abutment quantity between the valve closing limit stopper 62a and the full-closed stopper 58a is adjusted to be a half pitch.
When manufacturing a rotor core 69, which is integrally incorporated with the sleeve 62 and the bushing 68 as shown in FIG. 6, and is arranged in the central portion of the rotor 64 of the motor-driven valve 50 described above, as shown in FIGS. 7A to 7C, an openable/closable die device 71 defining a molding recess 73 for the sleeve 62 was conventionally used. A lower die 72 of the die device 71 is provided with a molding recess 72a for the valve closing limit stopper 62a, and a pin attaching hole 72c that opens in the central portion of the molding recess 73, and is provided with a key ridge 72b on the inner circumference thereof, and to the pin attaching hole 72c of the lower die 72 is set a set pin 74 to which a bushing 68 is screwed and secured through the engagement of the key ridge 72b with a key groove 74a, which is formed on a lower end circumference of the set pin 74, such that the state shown in FIG. 7C is obtained after the sleeve 62 is molded (such that a thread-cut leading end 68b of the female screw 68a of the bushing 68 is positionally aligned with the molding recess 72a for the valve closing limit stopper 62a), the prescribed distance h4 that is integer times as the pitches of the female screw 68a is maintained between a pin stepped portion 74b, to which a bottom face 68c of the bushing 68 abuts, and an inner bottom face of the stopper molding recess 72a, and then the die device 71 is closed. Then, molten resin is cast into the molding recess 73 so as to form the rotor core 69 as shown in FIGS. 7B and 7C, in which the bushing 68 and the sleeve 62 are integrally incorporated.
In addition, as to a rotor feed screw 70 also, in the same manner as described above and shown in FIGS. 8A to 8C, a die device 80 defining a molding recess 82 for the flange body 58 was used. A lower mold 81 of the die device 80 is provided with a molding recess 81a for the full-closed stopper 58a, and a bushing attaching hole 81c that opens in the central portion of the molding recess 82 and has a key ridge 81b at an inner bottom face, and to the bushing attaching hole 81c of the lower mold 81 is set a cylindrical set bushing 83 with a bottom to which a male screw pipe 61 is screwed and secured, as shown in FIG. 8A through the engagement of the key ridge 81b with a key groove 83a, which is formed on the lower portion of the set bushing 83, such that a thread-cut leading end 61b of the male screw 61a is positionally aligned with the stopper molding recess 81a, and a base end attaching portion 61c of the male screw pipe 61 projects above the lower mold 81. Then, the die device 80 is closed, and molten resin is cast into the molding recess 82 so as to form the rotor feed screw 70 as shown in FIGS. 8B and 8C, in which the male screw pipe 61 and the flange body 58 are integrally incorporated.
As mentioned above, conventionally, in order to manufacture the rotor core 69 and the rotor feed screw 70, the set pin 74 and the set bushing 83 were prepared, and these were incorporated with the bushing 68 and the male screw pipe 61, and then molten resin was required to be cast with the die device 71 and the die device 80, so that it took much time to manufacture the rotor core 69 and the rotor feed screw 70, resulting in increased manufacturing cost of the motor-driven valve 50.